If you close your eyes and listen to some shark tales, you could imagine sharks as mythical creatures, larger than life, like Loch Ness or Bigfoot, their legends becoming more fantastical with each telling. Somehow the falsehoods perpetuated about sharks over the centuries, along with outrageous thriller fiction movie claims, have interwoven with actual information about these magnificent big fish. To separate myth from reality, Discovery contacted Samuel Gruber, a professor of marine biology at the University of Miami's Rosenstiel School of Marine and Atmospheric Science and one of the world's leading shark experts. Here is his take on some common beliefs about sharks.
1. Sharks intentionally seek out human prey.
"There is no evidence that sharks preferentially go after humans," Gruber said. He mentioned that of the 80 some million water-activity participants each year, only a handful succumb to shark attacks. He cited reports issued by the National Safety Council that track the odds of dying from certain injuries. While you have a 1 in 4,473 chance of dying from falling out of a bed, chair or other furniture, sharks did not even make the list. Contact by hornets, wasps, bees and dogs, however, were significant enough to warrant mentions.
Gruber suggested that in the rare instances when sharks do attack humans, usually it is a case of mistaken identity. During World War II, for example, the USS Indianapolis sunk in shark-infested waters. Many men wound up injured or killed by the sharks. "In massive air/sea accidents, there can be a lot of blood, noise and unprotected people in the water," he said. "To a shark, this strange abundance of food must appear like a bunch of damaged turtles."
2. Sharks go after surfboards.
In this case, there is some truth to the statement, but only for certain shark species. Gruber said the great white does appear to look at silhouettes from below. He thinks the shape of some surfboards fools the sharks into believing they are viewing a pinniped, such as a seal, walrus or sea lion. Gruber is quick to point out that "far more surfers drown or die from other causes each year," so the chances of a surfer being taken out by a shark are still minimal.
3. Sharks do not attack at midday.
Gruber said this is a classic case of people taking human data and applying it to sharks. "Since fewer attacks occur at midday, we've come up with this notion that sharks tend not to attack at this time," he said. "In reality, what happens is that people usually go out to lunch then and are not in the water as much." He said the statement is like saying that individuals who own Toyotas and Chevrolets are more vulnerable to sharks, based on the statistics. "What we're really looking at is the fact that more humans simply own these types of cars. It has nothing to do with sharks."
4. Sharks do not have enemies.
Wrong! "Killer whales occasionally take sharks," Gruber said. Parasites are responsible for numerous shark deaths each year. Even sharks eat other sharks. Bull and tiger sharks particularly are known for this, and may kill their own pups, somewhat similar to how male cats can kill kittens. "Humans are by far the greatest enemy of sharks, though," he said. A 2006 study in the journal Ecology Letters determined humans kill 73 million sharks a year. That is just as a result of the shark-finning trade alone. Researchers calculated that 1.7 tons of shark meat are harvested each year.
5. Sharks are mindless eating machines.
Gruber said, "A lot of people think sharks only kill, eat and reproduce. Depending on how we look at the data, the same could be said for humans." The reality is that sharks are big-brained fish whose mental capacities fall in line with those measured for birds and mammals. "A shark could learn the Pavlovian response (conditioned training) faster than a cat or rabbit," he said.
With these and other myths, Gruber admits part of the problem is we still know so little about these fascinating, mysterious creatures. "When we don't know something, we tend to fall back on myths," he explained. He hopes the knowledge pendulum will swing more toward science in the years to come.